1. Field of the Invention
The present invention relates to image formation, and particularly to an image forming system, a recording medium on which an image forming program is recorded and an image forming apparatus, which can avoid duplicated image formation by the image forming apparatus.
2. Description of the Related Art
There has been a conventional technique with which an image forming apparatus is provided on a network, print data and print setting information are transmitted from a terminal connected to the network to the image forming apparatus, and the image forming apparatus accordingly performs image forming operation (printing).
Further, as a storage device has a higher capacity in these years, there has also been found a technique with which print data for example is stored in a storage device of an image forming apparatus and the image forming apparatus performs image forming operation according to information about a newly transmitted instruction to print.
Such techniques including storage of print data for example in the storage device of the image forming apparatus are advantageous in that it is unnecessary to transmit print data for example in a printing process (image forming process), which can save some work of the user in the printing process. There could arise, however, the state where an enormous amount of data is stored in the storage device.
In order to avoid such a state as described above, a product has been developed that automatically erases data stored in the storage device for a predetermined period (three days for example) from the time when image forming operation is done.
Various techniques have also been disclosed for avoiding storage of the same data in a storage device. For example, according to a technique disclosed in Japanese Laid-Open Patent Publication No. 10-143638 (Document 1), in response to an instruction to output image data already stored in an image processing apparatus, the image processing apparatus outputs the stored image data. According to a technique disclosed in Japanese Laid-Open Patent Publication No. 2006-239932 (Document 2), in the case where data that is input to be processed by an image forming apparatus is data that has already been stored, the stored data is overwritten with the input data.
Further, a conventional technique is disclosed of taking an action to inhibit image forming operation for the same data. For example, according to a technique disclosed in Japanese Laid-Open Patent Publication No. 2003-076519 (Document 3), under the conditions that a printer receives a print job and the same print job as the received print job is stored in the printer, information about this status is given. According to a technique disclosed in Japanese Laid-Open Patent Publication Nos. 2002-351634 (Document 4) and 2003-248570 (Document 5), in the case where the same print jobs are supplied to a printer, control is done such that the later supplied print job is inhibited.
As described above, by avoiding storage of the same data or inhibiting printing of the same data, it seems that storage of redundant data in the storage device of the image forming apparatus can be appropriately avoided.
Depending on how it is determined that “these are the same data,” however, accurate determination may not be made or the determination may take a long time, resulting in another problem that the user feels inconvenient. For example, if the whole image data to be printed out are compared with each other, a long time is consumed, which causes inconvenience for the user. In the case where only one of character data and image data are compared to determine whether they are the same data as disclosed in Document 5, it is determined that these data are the same image data even if the other of the character and image data are different, and thus accurate determination is not made.
Thus, the conventional techniques trying to avoid image formation of the same file in an image forming apparatus have the problem that whether or not these are the same data cannot be determined accurately or the determination takes a long time.